The production of malting barley under dryland and irrigated environments in South Africa (SA) has increased recently, making it the second most important winter crop after wheat. To assess the potential vulnerability of adapted barleys from SA to wheat stem rust (caused by Puccinia graminis f. sp. tritici, Pgt, race PTKST) and rye stem rust (Puccinia graminis f. sp. secalis, Pgs, isolate UVPgs1), 50 accessions were evaluated as seedlings and as adult plants. The same barley germplasm was tested against Pgt and Pgs cultures from the USA that have proven useful for detecting the stem rust resistance genes Rpg1 and the rpg4/Rpg5 complex. The possible presence of these resistance genes was assayed using molecular markers and sequence analysis. Barley accessions exhibited mostly resistant infection types (ITs) to the South African cultures, whilst field data revealed that several of the barley varieties displayed high severities in combination with more compatible host response types to race PTKST. The barley accessions exhibited mostly high ITs to cultures from the USA. None of the seedling IT data was sufficiently distinct to reliably postulate the presence of possible resistance genes. This result was corroborated from the molecular assays for Rpg1 and rpg4/Rpg5. Except for one line that tested heterozygous for the Rpg1 gene, none of the test entries contained this gene or a functional rpg4/Rpg5 complex due to the prevalence of mutations in the rpg4/Rpg5 + carriers. Susceptibility among barley varieties to wheat stem rust race PTKST under field conditions in the present study is of concern.

中文翻译：

---

南非麦芽大麦茎锈病抗性的评估和展望

南非（SA）旱地和灌溉环境下麦芽大麦的产量最近有所增加，使其成为仅次于小麦的第二大冬季作物。评估来自 SA 的适应大麦对小麦茎锈病（由小麦茎锈病，Pgt，小种 PTKST 引起）和黑麦茎锈病（Puccinia graminis f.sp. secalis，Pgs，分离株 UVPgs1）的潜在脆弱性，50种质被评估为幼苗和成株。针对来自美国的 Pgt 和 Pgs 培养物测试了相同的大麦种质，这些培养物已证明可用于检测茎锈病抗性基因 Rpg1 和 rpg4/Rpg5 复合物。使用分子标记和序列分析来测定这些抗性基因的可能存在。大麦种质主要表现出对南非文化的抗性感染类型 (ITs)，而现场数据显示，几个大麦品种表现出高严重性，并且与更兼容的宿主对 PTKST 种族的反应类型相结合。大麦种质主要表现出对来自美国的文化的高 IT。没有任何幼苗 IT 数据明显不同，无法可靠地假设存在可能的抗性基因。这一结果得到了 Rpg1 和 rpg4/Rpg5 的分子检测的证实。除了测试 Rpg1 基因杂合的一个品系外，由于 rpg4/Rpg5 + 携带者中的突变普遍存在，没有一个测试条目包含该基因或功能性 rpg4/Rpg5 复合物。在本研究中，大麦品种在田间条件下对小麦茎锈病 PTKST 的易感性令人担忧。